Catalyst for the simultaneous selective hydrogenation of diolefins and nitriles and method of making same

ABSTRACT

A catalyst useful for the simultaneous and selective hydrogenation of diolefins and nitriles present in a hydrocarbon feedstock. The support material is preferably selected from the group consisting of an inorganic oxide-zeolite composite, carbon and zeolite. A catalytically active phase is deposited on the support material. The catalytically active metal phase is selected from the group consisting of partially reduced Group IB metals and completely reduced Group VIII metals. The catalytically active metal phase is present in an amount of ≧0.03 wt %.

This is a division of application Ser. No. 08/354,969 filed Dec. 13,1994, now U.S. Pat. No. 5,523,271.

BACKGROUND OF THE INVENTION

The present invention relates to a catalyst material for use in thehydrogenation of hydrocarbon feedstocks and, more particularly, acatalyst which is useful for the simultaneous and selectivehydrogenation of diolefins and nitriles present in a hydrocarbonfeedstock.

There are known in the prior art processes in catalysts forhydrogenating unsaturated compounds in liquid hydrocarbon feedstocks.For example, U.S. Pat. No. 4,152,351 discloses a process for thehydrogenation an olefinic unsaturation. More specifically, it relates tothe catalytic hydrogenation of aliphatic, unsaturated compound in thepresence of a palladium hydrogenation catalyst on a suitable support.Still more specifically, the invention relates to the use of applicableadjuvants for a palladium hydrogenation catalyst used to hydrogenate theolefinic unsaturation. Further, the invention relates to thehydrogenation of aliphatic, unsaturated compounds containing nitrilegroups. U.S. Pat. No. 4,271,323 discloses a process for hydrogenatingunsaturated compounds in the liquid phase in the presence of a solublecatalyst obtained by reacting an organometal derivative or a metalhydride with a synergistic mixture of (a) a compound of zinc, zirconium,manganese, molybdenum, or iron and (b) a nickel or cobalt compound. U.S.Pat. No. 4,734,540 discloses a process which is useful for the selectivehydrogenation of polyunsaturated organic compounds. The resultantproduct of such a reaction produces the monoolefinic equivalents of thehydrogenated polyunsaturated organic compounds. The catalyst used inthis selective hydrogenation process comprises nickel and sulfurdeposited on the surface of an alumina support. The preferred catalystdoes not contain halogens, noble metals, alkaline earth metals, oralkali metals and is characterized by having only a very low percentageof the total pore volume being provided by pores having an average porediameter less than 150 angstroms. The great majority of the pore volumeis present in the form of macropores having diameters of 500 to 1500angstroms.

While the foregoing processes employ catalysts which are useful in thehydrogenation process, the processes and catalysts are not as selectivenor do they simultaneously hydrogenate diolefins and nitriles.Naturally, it would be highly desirable to provide a catalyst which isuseful for the simultaneous selective hydrogenation of diolefins andnitriles in a hydrocarbon feedstock.

Accordingly, it is the principle object of the present invention toprovide a catalyst useful for the simultaneous and selectivehydrogenation of diolefins and nitriles present in a hydrocarbonfeedstock.

It is a further object of the present invention to provide a method forpreparing a catalyst a aforesaid.

It is a still further object of the present invention to provide aprocess for the simultaneous and selective hydrogenation of diolefinsand nitriles from a hydrocarbon feedstock employing such a catalyst.

Further objects and advantages of the present invention will appearhereinbelow.

SUMMARY OF THE INVENTION

The present invention relates to a catalyst useful for the simultaneousand selective hydrogenation of diolefins and nitriles present in ahydrocarbon feedstock. The support material is preferably selected fromthe group consisting of an inorganic oxide-zeolite composite, carbon andzeolite. A catalytically active phase is deposited on the supportmaterial. The catalytically active metal phase is selected from thegroup consisting of partially reduced Group IB metals and completelyreduced Group VIII metals. The catalytically active metal phase ispresent in an amount of ≧0.03 wt %.

The catalyst of the present invention is particularly useful in aprocess for the simultaneous and selective hydrogenation of diolefinsand nitriles present in a hydrocarbon feedstock. The catalyst of thepresent invention is prepared by impregnating the support material witha solution of the active metal phase, drying the impregnated support andcalcining. The dried and calcined support is thereafter activated to theproper reduction state. The catalyst is used in a hydrogenation processwherein the hydrocarbon feedstock in the presence of the catalyst andhydrogen is treated at a temperature of between about 50° to 250° C. anda pressure of 150 to 650 psi so as to selectively hydrogenate diolefinsand nitriles from the hydrocarbon feedstock.

DETAILED DESCRIPTION

The catalyst of the present invention is particularly useful in aprocess for the simultaneous selective hydrogenation of diolefins andnitriles.

The catalyst of the present invention comprises a support materialhaving a catalytically active metal phase deposited thereon. Suitablesupport materials include inorganic oxide-zeolite composites, carbon andzeolite. A particular useful support material for use in the catalyst ofthe present invention is a composite alumina-zeolite material disclosedin U.S. Pat. No. 4,762,537 and sold under the trademark Selexsorb by theAluminum Company of America.

The support material has deposited thereon a catalytically active metalphase selected from the group consisting of Group IB metals and GroupVIII metals of the Periodic Table. Depending on the active metalemployed, the amount of the metal active phase present on the catalystmay vary. The active metal should be present in a minimum amount ofabout ≧0.03 wt % up to 20 wt %. Particularly suitable active metalmaterials include copper, nickel and palladium.

As noted above, particularly suitable support material for use in thecatalyst of the present invention is an alumina-zeolite composite soldby the Aluminum Company of America under the trademark Selexsorb. It hasbeen found that the surface area of the resulting catalyst should bebetween about 100 to 1500 m² /g, preferably between 100 to 1000 m² /gand ideally between about 250 to 350 m² /g. The pore volume of thecatalyst is preferably between 0.20 cc/g to 1.50 cc/g, preferably 0.30cc/g to 0.70 cc/g.

In order for the catalyst of the present invention to be effective inthe simultaneous selective hydrogenation of diolefins and nitriles, ithas been found that the metal active phase must be reduced to the rightstate in order to be effective. In accordance with the present inventionthe Group IB metals must be partially reduced while the Group VIIImetals must be completed reduced. By partial reduction it is meant thatmetal sites consist of one or more than one oxidation state differentthan zero, more particularly catalyst exhibit metal sites with a netcharge on them. By complete reduction it is meant the metal siteslargely consist on a single species, more particularly the highestnumber of species exhibit the elemental state of charge, i.e., 3000.

The catalyst of the present invention is prepared by impregnating thesupport material with a solution containing the catalytically activemetal phase. As noted above the metal active phase should be present inan amount on the final catalyst of about ≧0.03 wt %. The impregnatedsupport material is thereafter dried and calcined at a temperature ofbetween 150° and 600° C. for a time sufficient to decompose the metalsalt impregnated on the catalyst support. Particularly suitable metalsalts used in the aqueous solution for impregnating the catalystmaterial include Cu(NO₃)₂ *2.5 H₂ O; NiNO₃)₂, 6H₂ O; (CH₃ COO)₂ Pd. Thecalcined catalyst is thereafter activated to the proper reduction statedepending on the type of active metal phase employed. Partial reductionof the Group IB metals are accomplished under the following conditions:Temperature (°C.) 150-300, Pressure (psi) 15-150, H₂ flow rate (1t/h)0.1-8.0. Complete reduction of the Group VIII is achieved under thefollowing conditions: Temperature (°C.) 200-600, Pressure (psi) 15-150,H₂ flow rate (1t/h) 0.1-8.0.

The Catalyst of the present invention prepared in accordance with themethod described above is particularly useful in processes for thesimultaneous and selective hydrogenation of diolefins and nitriles froma hydrocarbon feedstock. The hydrocarbon feedstock in the presence ofthe catalyst is mixed with hydrogen wherein the ratio of the hydrogen tothe diolefins and nitriles in the feedstock is less than three timesstoichiometric amount required to selectively hydrogenate diolefins andnitriles. The hydrogen, hydrocarbon feedstock and catalyst are treatedin a reactor at a temperature of between 50° to 250° C. at a pressure ofbetween 150 to 650 psi. The preferred conditions for the hydrogenationprocess are a temperature of between 70° to 160° C. at a pressure ofbetween 200 to 400 psi at a liquid hourly space velocity of between 0.1to 5 h⁻¹, preferably 0.5 to 5 h⁻¹, ideally 1 to 4.5 h⁻¹.

The advantageous features of the catalyst of the present invention andmethod for preparing same will become clear from the following examples.

EXAMPLE 1

This example demonstrates the process for making the catalyst of thepresent invention employing an inorganic oxide-zeolite composite supporthaving a Group VIII activated metal phase deposited thereon.

An alumina-zeolite composite support of the type disclosed in U.S. Pat.No. 4,762,537 and sold by Alcoa Aluminum Corporation under the trademarkSelexsorb was selected as the catalyst support material. Four of thecatalysts supports were impregnated with solutions of nickel nitrate ofdifferent concentrations. A fifth catalyst was prepared by impregnatingthe catalyst support with palladium. The five impregnated datalysts weredried and calcined so as to decompose the salts of the incorporatedactive metal. The calcined impregnated catalysts supports were thenactivated under controlled temperature and time conditions so as tocompletely reduce or partially reduce the active metal phase. Forcomplete reduction, the catalysts were treated at a temperature of 450°C. at 250 psi for 8 hours. Partial reduction was carried out at 250° C.for 8 hours at 200 psi. Table 1 below sets forth the catalystcomposition and activation treatment for each of the five catalysts.

                  TABLE 1                                                         ______________________________________                                                             Active                                                   Catalyst  Support    Metal Phase  Activation                                  ______________________________________                                        1         alumina-   0.93 wt % Ni completely                                            zeolite                 reduced                                     2         alumina-   5.7 wt % Ni  completely                                            zeolite                 reduced                                     3         alumina-   5.7 wt % Ni  partially                                             zeolite                 reduced                                     4         alumina-   12.90 wt % Ni                                                                              completely                                            zeolite                 reduced                                     5         alumina-   0.30 wt % Pd completely                                            zeolite                 reduced                                     ______________________________________                                    

EXAMPLE 2

This example demonstrates the catalyst activity for the catalysts ofExample 1 for the simultaneous and selective hydrogenation of diolefinsand nitriles present in hydrocarbon feedstocks.

The activity for the simultaneous selective hydrogenation was determinedduring a 4 hour run using a synthetic C5 hydrocarbon feedstock havingthe composition set forth below in Table 2.

                  TABLE 2                                                         ______________________________________                                        Synthetic Feedstock Composition                                               ______________________________________                                               C5       97.5%                                                                Propilonitrile                                                                         0.5%                                                                 Diolefins                                                                              0.5%                                                                 Monoolefins                                                                            1.0%                                                          ______________________________________                                    

Eight cc's of each of the activated catalysts set forth in Example 1were employed in a reactor for treating the hydrocarbon feedstock ofTable 2. The reaction took place for 3 hours at a temperature of 120° C.and a pressure of 250 psi. The ratio by volume of hydrogen fed to thereactor with respect to the diolefins and nitriles was maintained at 3.The liquid space velocity (LHSV) of hydrogen feed was set at 3h⁻¹. Theresults for each run employing the catalysts of Example 1 are set forthherein below in Table 3.

                  TABLE 3                                                         ______________________________________                                                % Conversion % Conversion                                                                             % Conversion                                  Catalyst                                                                              Diolefins    Monoolefins                                                                              Nitriles                                      ______________________________________                                        1       100          59         86                                            2       100          78         100                                           3        0           0           0                                            4       100          0          100                                           5       100          0          88                                            ______________________________________                                    

As can be seen from Table 3 the concentration of the active metal phaseof the Group VIII metal employed have an affect on the selectivehydrogenation of the diolefins and nitriles in the hydrocarbon. Nickelconcentrations of below 6 wt % were insufficient to insure selectivehydrogenation. Catalyst 1 having a nickel concentration of 0.93 wt % wasin fact not selective. At the same time, as can be seen from the resultsemploying catalyst 5, 0.3 wt % palladium is sufficient for insuringselective hydrogenation of diolefins and nitriles. In addition, whencomparing the results obtained from hydrogenation of feedstocks withcatalysts 4 and 3, it can be seen that the Group VIII metals must becompletely reduced in order for the catalyst to be active for thehydrogenation of diolefins and nitriles. Specifically, catalyst 3 whichcontained 5.7 wt % nickel partially reduced did not achieve anyconversion of either olefins, monoolefins or nitriles.

EXAMPLE 3

This example demonstrates the process for making the catalyst of thepresent in invention employing an inorganic oxide-zeolite compositesupport having a Group IB active metal phase deposited thereon.

Four alumina-zeolite composite supports were impregnated with solutionsof copper nitrate of different concentrations. The four impregnatedcatalysts were dried and calcined so as to decompose the salts of theincorporated active metal. Three of calcined impregnated catalystsupports were activated by carrying out partial reduction of the activemetal phase at 250° C. for three hours. The fourth impregnated catalystsupport was completed reduced under the same conditions set forth in

                  TABLE 4                                                         ______________________________________                                                             Active                                                   Catalyst  Support    Metal Phase  Activation                                  ______________________________________                                        6         alumina-   0.79 wt % Cu partially                                             zeolite                 reduced                                     7         alumina-   5.9 wt % Cu  partially                                             zeolite                 reduced                                     8         alumina-   5.8 wt % Cu  completely                                            zeolite                 reduced                                     ______________________________________                                    

EXAMPLE 4

This example demonstrates the catalyst activity for the catalysts ofExample 3 for the simultaneous and selective hydrogenation of diolefinsand nitriles present in hydrocarbon feedstocks.

The synthetic feedstock set forth Table 2 of Example 2 was processedemploying the catalysts of Example 3 under the same conditions describedabove in Example 2. The results of each run employing the catalysts ofExample 3 are set forth hereinbelow in Table 5.

                  TABLE 5                                                         ______________________________________                                                % Conversion % Conversion                                                                             % Conversion                                  Catalyst                                                                              Diolefins    Monoolefins                                                                              Nitriles                                      ______________________________________                                        6       98           0          21                                            7       99           0          82                                            8        0           0           0                                            ______________________________________                                    

As can be seen from Table 5, as was the case with the Group VIII metalsdiscussed above, the concentrations of the active metal phase of theGroup IB metals employed have an affect on the selective hydrogenationof the diolefins and nitriles in the hydrocarbon. Copper concentrationsas low as 0.80 wt % were effective for the selective and simultaneoushydrogenation of diolefins and nitriles. In addition to the foregoing,the degree of reduction of the metal phase affects the activity of theGroup IB metal. However, contrary to the Group VIII metals, the Group IBmetals are effective when partially reduced and ineffective whencompletely reduced. In this regard see Catalyst No. 8 wherein the coppermetal phase was completely reduced and no conversion of diolefins,monoolefins or nitriles was accomplished.

EXAMPLE 5

This example demonstrates the importance of the catalyst support on theactivity of the catalyst of the present invention.

Carbon granules provided by Johnson Matthey were selected as onecatalyst support. A second catalyst support comprising gamma aluminasold by Johnson Matthey under was likewise selected. Both of thesupports were impregnated with palladium in the manner described abovewith regard to Example 1 and the impregnated catalyst supports were thenactivated by complete reduction at a temperature of 450° C., a pressureof 250 psi for eight hours. Table 6 below sets forth the catalystcomposition and activation treatment for each of the two catalysts.

                  TABLE 6                                                         ______________________________________                                                            Active                                                    Catalyst  Support   Metal Phase Activation                                    ______________________________________                                         9        gamma     1.0 wt % Pd completely                                              alumina               reduced                                       10        carbon    0.3 wt % Pd completely                                                                    reduced                                       11        gamma     0.3 wt % Pd completely                                              alumina               reduced                                       ______________________________________                                    

EXAMPLE 6

In order to demonstrate the catalyst activity for the catalysts ofExample 5 for the simultaneous and selective hydrogenation of diolefinsand nitriles, the synthetic feedstock of Example 2 was treated with thecatalysts under the same conditions set forth in Example 2. The resultsfor each run employing the catalysts of Example 5 are set forth below inTable 7.

                  TABLE 7                                                         ______________________________________                                                % Conversion % Conversion                                                                             % Conversion                                  Catalyst                                                                              Diolefins    Monoolefins                                                                              Nitriles                                      ______________________________________                                         9      100          88         18                                            10      100           0         50                                            11      100          30         20                                            ______________________________________                                    

The carbon supported catalyst, catalyst 10, was effective for thesimultaneous hydrogenation of diolefins and nitriles in a selectivemanner wherein the gamma alumina supported catalysts (9 and 11) achievedno selective conversion of diolefins, monoolefins or nitriles. Theresults lead one to conclude that carbon and the zeolite present in theinorganic oxide-zeolite composite are effective catalyst supports forthe catalysts of the present invention. Both the zeolite and carboncontain moderate Lewis acid sites which are believed to be responsiblefor the superior activity characteristics of the catalysts of thepresent invention.

This invention may be embodied in other forms or carried out in otherways without departing from the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims, and all changes which comewithin the meaning and range of equivalency are intended to be embracedtherein.

We claim:
 1. A process for the simultaneous and selective hydrogenationof diolefins and nitriles from a hydrocarbon feedstock comprising:(a)providing a hydrocarbon feedstock having a diolefin content of ≧0.1 wt %and a nitrile content of ≧2 ppm(w); (b) providing a catalystcomprising1) a support material selected from the group consisting of aninorganic oxide-zeolite composite, carbon and zeolite; and 2) acatalytically active metal phase selected from the group consisting ofpartially induced Group IB metals and completely reduced Group VIIImetals, said active metal being present in an amount of about ≧0.03 wt%; (c) mixing the hydrocarbon feedstock in the presence of the catalystwith hydrogen wherein the ratio of hydrogen to the diolefins andnitriles in the feedstock is less than three times the stoichiometricamount required to selectively hydrogenate the diolefins and nitriles;and (d) treating the feedstock and hydrogen mixture in the presence ofthe catalyst at a temperature of about between 50° to 250° C. at apressure of about between 150 to 650 psi.
 2. A process according toclaim 1 wherein said temperature is between about 60° to 160° C.
 3. Aprocess according to claim 2 wherein the pressure is between 200 to 400psi.
 4. A process according to claim 1 wherein the liquid hourly spacevelocity is in the range of between about 0.1 to 5 h⁻¹.
 5. A processaccording to claim 1 wherein the liquid hourly space velocity is in therange of between about 0.5 to 5 h⁻¹.
 6. A process according to claim 1wherein the liquid hourly space velocity is in the range of betweenabout 1 to 4.5 h⁻¹.